Some mothers will be able to check from tomorrow whether their partners are convicted sex offenders. Under pilot projects being introduced in response to demands for a 'Sarah's Law', individuals will be given greater information about paedophiles living in their area.

But public protection experts and children's charities have questioned the value of the projects. They warn that the sharing of the information could lead to mob justice and cause paedophiles to adopt lower profiles, making them more difficult to monitor.

The pilots will be run by four police forces over the next year in Warwickshire, Cambridgeshire, Cleveland and Hampshire, during which the government will assess their value. Parents and guardians will be able to request limited information about people who come into close contact with their children.

But it will be up to local authorities and police forces to consider the request and to decide what information, if any, they will disclose. Those who receive confidential information will be warned not to share it with others. 'We will have to wait and see if the pilot programmes help to keep children safe from sex offenders and do not just create a false sense of security,' said Diana Sutton, head of policy at the NSPCC. 'We strongly urge people to remain alert to the fact that not all child abusers have criminal records, because many are not caught and charged with an offence. Someone might be given a clean bill of health by police because they do not have a criminal record, but may still pose a threat to children.

'Disclosing information to specific parties is just one strand of a wider management system which still lacks proper funding and manpower.'

'Sarah's Law', named after Sarah Payne, the eight-year-old girl who was murdered by the convicted paedophile Roy Whiting in 2000, is partly inspired by Megan's Law in the US, brought in after the rape and murder of Megan Kanka, seven, in 1994.

Under Megan's Law, individual states decide what information will be made available about paedophiles and how it will be disseminated. The information that can be shared with local communities includes the offender's name, picture, address and nature of their crime. Often the information is displayed on public websites, in newspapers and in leaflets through letterboxes.

Sarah's parents, Sara and Michael, have insisted that, if a Megan's Law had been operating in the UK, their daughter would not have died. Their argument was taken up by the News of the World, which launched a campaign to have the law introduced to the UK.

In response, John Reid, then Home Secretary, promised last year that the government would introduce the pilot schemes as part of a 'radical' package to protect young people. He said the pilots would introduce a 'presumption' that police would tell a mother that her partner was a registered sex offender.

At the time he denied the initiative was a form of Megan's Law, which goes much further in sharing information with a local community than is intended with the four UK pilot projects. 'What we did want to do was address the campaign that Sara Payne put forward among others. If someone wants to call that Sarah's Law, then I am delighted for her.'